1. Field of the Invention
The present invention relates to an improved chuck, particularly to a keyless chuck which allows to hold and release a tool.
2. Description of Related Art
Electrically or pneumatically driven tools, like screw drivers, drills and grinding wheels, have been in use for a long time. The tools have shanks with various diameters and cross-sections. To hold those tools, chucks with adjustable widths are employed.
A conventional chuck has a main body containing three jaws, which are arranged obliquely around a central axis, separated by angles of 120 degrees. The jaws have threads which are engaged with the inner thread of a nut. Turning the nut by a toothed wheel on the main body causes the jaws to move closer together or farther apart for adjusting to different diameters of tools to be held.
Recently, keyless chucks have been designed. In a keyless chuck, a ball bearing reduces friction, when the nut is turned, allowing the user to turn the nut directly manually. Assembling the keyless chuck, especially the ball bearing, however, is not easy.
For this reason, the prior art has disclosed a chuck, wherein the nut and the ball bearing are connected by a coupling element, thus facilitating the assembly of the chuck.
However, there is still some need for improvement. For fixing the nut, the chuck has a holding ring, which is pressed on the main body or screwed thereon. This complicates the assembly of the chuck. Furthermore, the chuck has a front cover, pressed on the nut. Since the nut is not fixed, but slightly shaky, the front cover is easily shaken, too. When the front cover is set on the nut, additional pressure has to be applied. The inner diameter of the front cover is slightly smaller than the outer diameter of the nut, so the front cover is easily deformed or positioned wrongly.